In September the United Nations will finalize a new package of development goals that will guide the efforts of its member states to improve living conditions around the world. The 17 Sustainable Development Goals (SDGs) are long on ambition — they intend to “end poverty in all its forms everywhere” by 2030 — but short on substance. Most importantly, the SDGs’ approach to education is insufficient.

Expanding quality education is the only feasible way to generate long-term economic growth, which is why a strong and coherent emphasis on education is central to the success of the global development agenda. Unfortunately, the current SDG goal to “ensure inclusive and equitable quality education” is too vague and provides no guidance for measuring increases in cognitive skill levels. The global development community can do better.

Recognizing the importance of education, the prior Millennium Development Goals included a target of reaching universal primary schooling by 2015. Although developing countries did, in fact, substantially expand access to schooling over the past two decades, many have still not translated increased education into economic well-being. The reason is that too many countries focused on increasing the number of children attending school rather than on educational outcomes.

Knowledge capital is not measured by school attendance, and increased access to schools alone turns out to be an incomplete and ineffective goal for development. In recent research, we have shown that even in middle-income countries, where the primary school completion averages just 75 percent, the economic gains from improving the quality of schools without trying to increase enrollment are three times as large as those from expanding enrollment without improving quality. Instead of simply expanding access to schooling, then, the central post-2015 goal for education should be that “all youth achieve at least basic skills.”

The projected economic gain from ensuring that everyone has basic skills is remarkable for all countries, across all income levels. But unsurprisingly, countries with the lowest incomes, where current enrollment and achievement rates have the most room for growth, would gain the most. Across the 31 middle-income countries for which data exist, the economic gains from achieving universal basic skills would average more than eight times their current GDP.

Even high-income countries, which have generally been left out of development discussions, would benefit from universal basic skills. Although most of these countries have achieved nearly universal access to primary and secondary schools, many of their citizens still fail to achieve basic skills. For the high-income OECD countries, an average of 20 percent lack basic skills. For high income non-OECD countries, including four Arab oil-rich states, 36 percent fail to reach Level 1 on the Programme for International Student Assessment (PISA) tests.

The central post-2015 goal for education should be that ‘all youth achieve at least basic skills.’ Given the potential gains, it is important that the SDGs focus more clearly on improving cognitive skills. The most important step would be for the United Nations to establish an explicit quality goal, one that can be tracked by measured skills — such as Level 1 in mathematics and reading for 15-year-olds on PISA, or its equivalent, which represents the basic level of math and reading skills of the type required for participation in a competitive world economy. This goal implies linking both national educational policies and international support to student outcomes observed through regular assessments of students’ skills. Such assessments would support strong accountability systems and can drive policies such as the upgrading of teacher quality that have proven effective worldwide.

The inclusive growth made possible through universal achievement of basic skills has tremendous potential to reduce poverty, improve health, facilitate gender equity, and foster new technologies needed to ensure sustainable growth. There is no substitute for improved skills, and efforts to improve them must start with measuring the right metric. It is not always true that ‘what gets measured gets done’. But it is more universally true that ‘what does not get measured does not get done’.